不同拉结构造填充墙框架抗震性能试验研究

开展了3榀足尺空心砌块填充墙框架的低周往复加载试验.主要研究填充墙的不同拉结构造形式对填充墙框架抗震性能的影响.填充墙钢筋拉结构造包括常规拉结、通长拉结和配筋砂浆带拉结等3种形式.在试验研究基础上分析了试件的破坏形态、滞回特性、骨架曲线和耗能能力等特征.研究结果表明,3种拉结构造的填充墙均经历了开裂、裂缝贯通和砌块剥落和塌落等破坏阶段.与常规拉结填充墙相比,采用钢筋通长拉结或配筋砂浆带拉结可延缓填充墙开裂和破碎,在大位移角下表现出较好的抗倒塌能力和耗能能力.在1/25位移角时,钢筋通长拉结的填充墙砌块剥落面积最小,体现了更好的拉结效果.

超高页岩清水砖装饰外墙的施工

针对超高页岩清水砖装饰外墙因高厚比超过规范要求时,常规配筋构造不能满足墙体砌筑稳定性、装饰墙面与主体结构需加强拉结的问题,从加强拉结构造、设置砌筑基础及压顶两个角度进行了防倾覆措施设计。通过对页岩清水砖开孔进行深化、穿孔钢筋连接接长深化,以及页岩清水砖排布模拟深化等措施进行优化,解决了超高页岩清水砖装饰外墙施工问题。总结的经验可供类似工程参考。

Microstructures and mechanical properties of Mg-10Ho-0.6Zr-xNd alloys

Mg-10Ho-0.6Zr-xNd (x=0, 1, 3 and 5, mass fraction, %) alloys were prepared by metal mould casting, and the microstructures and mechanical properties were investigated. The results show that the grain size of as-cast alloys reduces and the hardness and strength increase with the increase of Nd content. The alloys are aged followed by solid solution treatment. Mg-10Ho-0.6Zr-3Nd and Mg-10Ho-0.6Zr-5Nd alloys exhibit obvious age hardening response. The hardness value of Mg-10Ho-0.6Zr-5Nd alloy increases from HV104 at as-cast state to HV136 at peak-aged state. The maximum ultimate tensile strength and yield strength of the Mg-10Ho-0.6Zr-5Nd alloy are obtained in at peak-aged state, and the values are 323 MPa, 212 MPa at room temperature, and 258 MPa, 176 MPa at 250 ℃, respectively. The improvement of the tensile strength is mainly attributed to the fine and dispersively distributed plate-shaped β′ metastable phase.

Upper mantle anisotropy of the eastern Himalayan syntaxis and surrounding regions from shear wave splitting analysis

Polarization analysis of teleseismic data has been used to determine the XKS(SKS,SKKS,and PKS)fast polarization directions and delay times between fast and slow shear waves for 59 seismic stations of both temporary and permanent broadband seismograph networks deployed in the eastern Himalayan syntaxis(EHS)and surrounding regions.The analysis employed both the grid searching method of the minimum tangential energy and stacking analysis methods to develop an image of upper mantle anisotropy in the EHS and surrounding regions using the newly obtained shear wave splitting parameters and previously published results.The fast polarization directions are oriented along a NE-SW azimuth in the EHS.However,within the surrounding regions,the fast directions show a clockwise rotation pattern around the EHS from NE-SW,to E-W,to NW-SE,and then to N-S.In the EHS and surrounding regions,the fast directions of seismic anisotropy determined using shear wave splitting analysis correlate with surficial geological features including major sutures and faults and with the surface deformation fields derived from global positioning system(GPS)data.The coincidence between structural features in the crust,surface deformation fields and mantle anisotropy suggests that the deformation in the crust and lithospheric mantle is mechanically coupled.In the EHS,the coherence between the fast directions and the NE direction of the subduction of the Indian Plate beneath the Tibetan Plateau suggests that the lithospheric deformation is caused mainly by subduction.In the regions surrounding the EHS,we speculate that a westward retreat of the Burma slab could contribute to the curved anisotropy pattern.The Tibetan Plateau is acted upon by a NE-trending force due to the subduction of the Indian Plate,and also affected by a westward drag force due to the westward retreat produced by the eastward subduction of the Burma slab.The two forces contribute to a curved lithospheric deformation that results in the alignment of the upper mantle peridotite lattice parallel to the deformation direction,and thus generates a curved pattern of fast directions around the EHS.

Structural feature and its significance of the northernmost segment of the Tertiary Biluoxueshan-Chongshan shear zone,east of the Eastern Himalayan Syntaxis

Here we describe ductile, ductile-brittle and brittle deformation styles in the northern segment of the Tertiary Biluoxue- shan-Chongshan shear zone lying to the east of the Eastern Himalayan Syntaxis. In the northernmost part of the zone in the vi- cinity of the Eastern Himalayan Syntaxis, it consists of mylonitic gneiss, granite, and schist. Based on field relations and min- eral assemblages, the rocks are classified into gneiss belt in the west limb, including banded gneiss, augen mylonite and mig- matite gneiss, and schist belt in the east limb. Except for the massive granite pluton, the other three tectonites are affected by polystage deformation （D1-D4）. Fold deformation of the first stage D1 is isoclinal to tight pattern with nearly N-S fold axes and steeply axial planar cleavage S 1, which resulted in the local crustal thickening under a contractive setting. D2 overprinted D1 and is characterized by tight folds with steep axes and N-S fold axial planar, which are also characterized by large-scale ductile strike-slip shear foliation $2, parallel to the nearly N-S trending axial planes of D1 and D2. The structural pattern of D2 represents a transpression along the zone. D3 occurred during the late stage of the transpression or post-transpression, produc- ing the NW-SE and NE-SW trending strike-slip faults of the third stage D3. Following the D3 deformation, the zone was ex- humed to shallow crustal level where the various tectonites underwent a brittle transtensional deformation D4, combined with one N-S trending strike-slip component and one normal faulting component. Structures and previous geochronologies pre- sented in the paper suggest that the study area is correlated with those in the adjacent tectonic zones, Ailaoshan-Red River shear zone and Gaoligong shear zone in the western Yunnan. It underwent intensive polyphase deformation, namely, crustal thickening, transpression, and transtension, responding to syn-collision and post-collision of India-Eurasia from 65 Ma to cur- rent period east of the Eastern Himalayan Syntaxis.

Anatomy of composition and nature of plate convergence： Insights for alternative thoughts for terminal India-Eurasia collision

The pattern and timing of collision between India and Eurasia have long been a major concern of the international community. However, no consensus has been reached hitherto. To explore and resolve the disagreements in the Himalayan study,in this paper we begin with the methodology and basic principles for the anatomy of composition and nature of convergent margins,then followed by an effort to conduct a similar anatomy for the India-Eurasia collision. One of the most common patterns of plate convergence involves a passive continental margin, an active continental margin and intra-oceanic basins together with accreted terranes in between. The ultimate configuration and location of the terminal suture zone are controlled by the basal surface of the accretionary wedge, which may show fairly complex morphology with Z-shape and fluctuant geometry. One plausible method to determine the terminal suture zone is to dissect the compositions and structures of active continental margins. It requires a focus on various tectonic elements belonging to the upper plate, such as accretionary wedges, high-pressure(HP)-ultra-high-pressure(UHP) metamorphic rocks, Barrovian-type metamorphic rocks and basement nappes, together with superimposed forearc basins.Such geological records can define the extreme limits and the intervening surface separating active margin from the passive one,thus offering a general sketch for the surface trace of the terminal suture zone often with a cryptic feature. Furthermore, the occurrence of the cryptic suture zone in depth may be constrained by geophysical data, which, in combination with outcrop studies of HP-UHP metamorphic rocks, enables us to outline the terminal suture zone. The southern part of the Himalayan orogen records complicated temporal and spatial features, which are hard to be fully explained by the classic "two-plate-one-ocean" template,therefore re-anatomy of the compositions and nature for this region is necessitated. Taking advantage of the methodology and basic principles of plate convergence anatomy and synthesizing previous studies together with our recent research, we may gain new insights into the evolution of the Himalayan orogeny.(1) The Yarlung-Zangbo ophiolite is composed of multiple tectonic units rather than a single terminal suture zone, and a group of different tectonic units were juxtaposed against each other in the backstop of the Gangdese forearc.(2) The Tethyan Himalayan Sequence(THS) contains mélanges with typical block-in-matrix structures, uniform southwards paleocurrents and age spectra of detrital zircons typical of Eurasia continent. All of these facts indicate that the THS belonged to Eurasia plate before the terminal collision, emplaced in the forearc of the Gangdese arc.(3) The Greater Himalayan Crystalline Complex(GHC) and Lesser Himalayan Sequence(LHS) comprise complex components including eclogites emplaced into the GHC and the upper part of the LHS. Judging from the fact that HP-UHP metamorphic rocks are exhumed and emplaced in the upper plate, the GHC and the upper part of the LHS where eclogite occur should be assigned to the upper plate, lying above the terminal subduction zone surface. It is the very surface along which the continuous subduction of the India subcontinent occurred, therefore acting as the terminal, cryptic suture. From the suture further southward, the bulk rock associations of the LHS and Sub-Himalayan Sequence(Siwalik) show little affinity of mélange, probably belonging to the foreland system of the India plate. By the anatomy of tectonic features of all the tectonic units in the Himalayan orogen as well as the ages of the subduction-accretion related deformation, we conclude that the terminal India-Eurasia collision occurred after 14 Ma, the timing of the metamorphism of the eclogites emplaced into the upper plate. The development of rifts stretching in N-S direction in Tibet and tectonic events with the transition from sinistral to dextral movements in shear zones, such as the Ailaoshan fault in East Tibet, can coordinately reflect the scale and geodynamic influence of the India-Eurasia convergence zone.By conducting a detailed anatomy of the southern Himalayas, we propose a new model for the final collision-accretion of the Himalayan orogeny. Our study indicates that the anatomy of structures, composition, and tectonic nature is the key to a better understanding of orogenic belts, which may apply to all the orogenic belts around the world. We also point out that several important issues regarding the detailed anatomy of the structures, compositions and tectonic nature of the Himalayan orogeny in future.